The present invention generally relates to a utility knife of improved construction, and more particularly, to a utility knife which facilitates installation and replacement of the blade, and which provides for increased safety during use.
A variety of utility knives have been developed for use in any of a number of applications. Whether intended for use in the construction trades, for packaging and shipping, for carpet installation, or some other purpose, it is in each case important for the knife to exhibit properties including safety, reliability and convenience in use. Moreover, to achieve public acceptance of the product, these characteristics must be delivered in a cost effective product.
In practice, it has been found that these several requirements often tend to conflict with one another. For this reason it is not uncommon for a particular design to sacrifice one of the above-mentioned factors in favor of another.
As an example, U.S. Pat. No. 5,301,428 (Wilcox) discloses a utility knife comprised of two mating halves joined at a central pivot to provide access to the active blade (for insertion and replacement) and a quantity of stored replacement blades. The end of the handle which is to receive the active blade is provided with paired tongues and slots for interlocking the mating halves of the handle when closed for use, to make sure that the blade is securely held in position during use.
However, the safety of the resulting closure is achieved at the expense of convenience in use, and overall cost. In practice, the pivoting mechanism of the handle is relatively cumbersome to operate when it becomes desirable to access the active blade. It has also been found to be relatively difficult to access the stored blades, and to install a replacement blade, without either the active blade or the replacement blade (or blades), or both, falling from the handle while such blade replacement is in progress. The potential for the active blade to fall from the handle during replacement exists even in the presence of a magnet which is used to secure the handle's blade carrier. In practice, the separation which is present between the blade and the magnet is sufficient to allow the blade to fall from the carrier when the handle is opened, leading to a significant compromise in safety.
Another example is the utility knife disclosed in U.S. Pat. No. 5,022,156 (Kallens et al.), which is also comprised of two mating halves having structure for receiving an active blade and a quantity of stored replacement blades. The disclosed tool handle incorporates features which are intended to simplify blade replacement. To this end, a fastener assembly is provided to facilitate separation of the mating halves for purposes of gaining access to the active blade, and the replacement blades stored in the tool handle. However, the convenience afforded by the disclosed closure is achieved at the expense of safety.
In practice, the spring-biased fastener assembly has been found to allow significant separation of the halves of the tool, at times allowing the active blade to be pulled from the handle during use. This can cause an exposed blade to become embedded in the work surface, leading to a significant potential for injury. It has also been found that during the installation of an active blade, or when installing a replacement blade, either the active blade or the replacement blade (or blades), or both, can freely fall from the handle, again leading to a significant compromise in safety.
It has therefore remained to provide a utility knife which is not only convenient to use, but which is also capable of operating safely and reliably both when in active use, and during the installation or replacement of the active blade.